The present invention relates to a semiconductor integrated circuit device and a technique of manufacturing the same, more particularly, the present invention relates to a gate structure of a fine MISFET (Metal Insulator Semiconductor Field Effect Transistor) and a technique effectively applied to a method of manufacturing the same.
A so-called polymetal gate in which refractory metal such as tungsten is laminated on a polycrystalline silicon film is adopted in order to lower the resistance of the gate electrode of the MISFET.
Meanwhile, a so-called light oxidation treatment for forming a thermal oxide film on a sidewall of the gate electrode is performed in the etching of the gate electrode because a gate insulating film under the gate electrode is also caused to be etched in the etching so that the withstand voltage of the gate insulating film is deteriorated.
For example, the gazette of Japanese Patent Laid-Open No. 2001-36072 discloses a technique for preventing the oxidation of a metal layer by means of protecting the sidewalls of the metal layer composing the polymetal gate.
Also, the gazette of Japanese Patent Laid-Open No. 11-261059 discloses a technique for forming a low-resistance transistor with no metal contamination. According to this technique, the low-resistance transistor without metal contamination is formed by covering the exposed portion of a metal composing the polymetal gate of the transistor with a film of LPCVD-HTO or SiN9, and then by processing a polysilicon film 3 below it.
Also, in xe2x80x9cA fully working 0.14 xcexcm DRAM technology with polymetal (W/WNx/Poly-Si) gatexe2x80x9d by J. W. Jung et al. in the IEDM 2000 pp. 365-368, disclosed is a cleaning technique using H2SO4 and purified water performed after the etching for a gate electrode made of W/WNx and poly-Si.
The inventors have been engaged in the research and development of the data transfer MISFET and the DRAM (Dynamic Random Access Memory) including a data storage capacitor connected in series to the data transfer MISFET. The inventors had been examining the introduction of a polymetal gate electrode capable of lowering resistance in comparison to the conventional polycide gate into the gate electrode of the data transfer MISFET.
However, it had been frequently found that the product adopting such a polymetal gate structure has a tendency to increase the leak current. As a result, it had been difficult to adopt the polymetal gate for the product with severe restriction in the leak current value.
In such a circumstance, the inventors have intensely examined the increase of the leak current like this. As a result, the inventors have reached the conclusion that the diffusion of metal (metal contamination) composing the polymetal gate into the semiconductor substrate causes the increase of the leak current as described later in detail.
An object of the present invention is to reduce the leak current of the MISFET by reducing the contamination of the metal composing the polymetal gate.
Also, another object of the present invention is to improve the retention characteristic of a memory cell including the MISFET by reducing the leak current in the MISFET.
Also, another object of the present invention is to improve the performance of the semiconductor integrated circuit device having the MISFET by reducing the leak current in the MISFET. Still another object of the present invention is to improve the yield of the semiconductor integrated circuit device.
The above and other objects and novel characteristic of the present invention will be apparent from the descriptions and the accompanying drawings of this specification.
The typical ones of the inventions disclosed in this application will be briefly described as follows.
(1) A method of manufacturing a semiconductor integrated circuit device according to the present invention comprises the steps of: performing etching to remove a second insulating film, a refractory metal film, and a predetermined thickness of a silicon film, which are deposited on a first insulating film formed on a semiconductor substrate, so as not to expose the first insulating film; selectively forming a third insulating film on a sidewall of the silicon film and on a sidewall of the refractory metal film; removing a part of the silicon film not covered with the third insulating film; and performing a thermal treatment to a surface of the silicon film in an oxidation atmosphere.
(2) Also, a semiconductor integrated circuit device according to the present invention comprises: a first insulating film formed on a main surface of a semiconductor substrate; a silicon film formed on the first insulating film, which has a first sidewall on a part contacting to the first insulating film and a second sidewall on a part apart from the first insulating film; a refractory metal film formed on the silicon film and having a third sidewall; a second insulating film covering the second and third sidewalls; and a third insulating film positioned between the first and second insulating films and covering the first sidewall.
(3) Also, the semiconductor integrated circuit device is characterized in that the first and third insulating films are oxide films, and the second insulating film is a silicon nitride film.
(4) Also, the semiconductor integrated circuit device is characterized in that the first sidewall is at a position away from the second insulating film in comparison to the position of the second sidewall.
(5) Also, the semiconductor integrated circuit device is characterized in that the first and second sidewalls are almost perpendicular to the main surface of the semiconductor substrate.
(6) Also, the semiconductor integrated circuit device is characterized in that the silicon film is interposed between the third insulating film and the refractory metal film.
(7) Also, a semiconductor integrated circuit device according to the present invention comprises: a semiconductor substrate having a main surface; a pair of semiconductor regions formed over the main surface of the semiconductor substrate; a silicon film formed over the main surface of the semiconductor substrate via a first insulating film in a region between the pair of semiconductor regions; a refractory metal film formed on the silicon film; a second insulating film, which covers a sidewall of the refractory metal film and a sidewall of the silicon film; and a third insulating film, which covers a sidewall of the silicon film, wherein the third insulating film is at a position between the first insulating film and the second insulating film.
(8) Also, the semiconductor integrated circuit device is characterized in that the second insulating film is a silicon nitride film, and the first and third insulating films are silicon oxide films.
(9) Also, the semiconductor integrated circuit device further comprises: a fourth insulating film positioned on the refractory metal film, a sidewall of which is covered with the second insulating film.
(10) Also, the semiconductor integrated circuit device is characterized in that the second and fourth insulating films are silicon nitride films, and the first and third insulating films are silicon oxide films.
(11) Also, the semiconductor integrated circuit device is characterized in that, with respect to the direction from one semiconductor region to the other semiconductor region, a width of the silicon film close to the first insulating film is smaller than that of the silicon film close to the refractory metal film.
(12) Also, the semiconductor integrated circuit device is characterized in that, with respect to the direction from one semiconductor region to the other semiconductor region, a width of the silicon film close to the first insulating film is wider than that of the silicon film close to the refractory metal film.
(13) Also, the semiconductor integrated circuit device is characterized in that the silicon film is interposed between the third insulating film and the refractory metal film.